如何写sql语句每次返回next 50条;

如何写sql语句每次返回next 50条;
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不是用sql写的吧！用前台写更好。用sql不好写。
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create procedure pro(p_page in number,p_rc out test_age.mycursor)
as
str varchar2(100);
begin
str:='select * from table_name where rownum<=' ¦ &brvbarp_page
¦ ¦'minus'
¦ ¦'select * from table_name where rownum<=' ¦ &brvbarp_page-50;
open p_rc for str;
end;
/

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最好写在前台。